全文获取类型
收费全文 | 8602篇 |
免费 | 527篇 |
国内免费 | 28篇 |
专业分类
电工技术 | 132篇 |
综合类 | 6篇 |
化学工业 | 1777篇 |
金属工艺 | 323篇 |
机械仪表 | 585篇 |
建筑科学 | 168篇 |
矿业工程 | 1篇 |
能源动力 | 370篇 |
轻工业 | 627篇 |
水利工程 | 30篇 |
石油天然气 | 11篇 |
无线电 | 1745篇 |
一般工业技术 | 1825篇 |
冶金工业 | 623篇 |
原子能技术 | 149篇 |
自动化技术 | 785篇 |
出版年
2024年 | 5篇 |
2023年 | 111篇 |
2022年 | 151篇 |
2021年 | 276篇 |
2020年 | 211篇 |
2019年 | 182篇 |
2018年 | 240篇 |
2017年 | 267篇 |
2016年 | 312篇 |
2015年 | 223篇 |
2014年 | 336篇 |
2013年 | 541篇 |
2012年 | 550篇 |
2011年 | 668篇 |
2010年 | 481篇 |
2009年 | 500篇 |
2008年 | 472篇 |
2007年 | 369篇 |
2006年 | 331篇 |
2005年 | 303篇 |
2004年 | 276篇 |
2003年 | 236篇 |
2002年 | 251篇 |
2001年 | 211篇 |
2000年 | 203篇 |
1999年 | 197篇 |
1998年 | 307篇 |
1997年 | 182篇 |
1996年 | 140篇 |
1995年 | 94篇 |
1994年 | 99篇 |
1993年 | 79篇 |
1992年 | 43篇 |
1991年 | 55篇 |
1990年 | 38篇 |
1989年 | 32篇 |
1988年 | 28篇 |
1987年 | 29篇 |
1986年 | 17篇 |
1985年 | 13篇 |
1984年 | 12篇 |
1983年 | 14篇 |
1982年 | 10篇 |
1981年 | 14篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1977年 | 10篇 |
1976年 | 10篇 |
1975年 | 3篇 |
1974年 | 5篇 |
排序方式: 共有9157条查询结果,搜索用时 13 毫秒
251.
252.
Kim NK Cho S Lee SH Park HR Lee CS Cho YM Choy YH Yoon D Im SK Park EW 《Meat science》2008,80(4):1068-1073
Proteomic profiling by two-dimensional gel electrophoresis and mass spectrometry of longissimus dorsi muscle tissue from Korean native cattle identified seven proteins that are differentially expressed in animals producing low and high quality grade beef. The expression level of alpha actin is increased in high quality grade beef and the expression levels of T-complex protein 1 (TCP-1), heat shock protein beta-1 (HSP27), and inositol 1,4,5-triphosphate receptor type1 (IP3R1), a new protein to be associated with meat quality, are increased in low quality grade beef. In particular, the quantitation of HSP27 and IP3R1 by both silver staining and immunoblotting correlated well with intramuscular fat content, meat tenderness, and free calcium levels. The data suggest that HSP27 and IP3R1 are potential meat quality biomarkers and their identification provides new insight into the molecular mechanisms and pathways associated with overall beef quality. 相似文献
253.
Eun Jung Cho Xiang Lan Piao Moon Hee Jang Seung Hoon Baek Hyun Young Kim Ki Sung Kang Sung Won Kwon Jeong Hill Park 《Food chemistry》2008
This study was carried out to investigate changes in the free amino acid contents and antioxidant activity of Panax ginseng induced by steaming at different temperatures. For this purpose, white ginseng (WG), red ginseng (RG, ginseng steamed at 100 °C) and ginseng steamed at 120 °C (SG) were prepared using an autoclave. Most free amino acids were decreased significantly by steam treatment, with the greatest reduction observed in SG. Total content of free amino acids, 17.9 mg/g in WG was reduced to 12.2 mg/g in RG and 2.79 mg/g in SG. As for Arg which is the most predominant amino acid in ginseng, the content, 10.4 mg/g in WG, decreased significantly to 1.38 mg/g in SG. In particular, β-N-oxalyl-L-α,β-diaminopropionic acid (β-ODAP), a well-known neurotoxin, was reduced by 92.9% in SG. In contrast, the level of Maillard reaction products (MRPs) increased with steam treatment, which indicates that the reduction of most amino acids is attributed to the extent of the Maillard reaction. Based on MRPs being useful antioxidants, we assayed the scavenging activity against free radicals produced by 2,2′-azobis-(2-amidinopropane) dihydrochloride (AAPH). The radical scavenging activity of a ginseng extract increased with steam treatment, with the most potent activity in SG. Further, MRPs-rich fraction in SG showed powerful antioxidant activity, which indicates MRPs are major contributors to antioxidant activity enhanced by steam treatment. 相似文献
254.
Sung Ho Oh Jae Gun Han Young Kim Ji Hye Ha Seung Seop Kim Myoung Hoon Jeong Hyang Suk Jeong Na Young Kim Jeong Sub Cho Won Byong Yoon Shin Young Lee Do Hyung Kang Hyeon Yong Lee 《Journal of Bioscience and Bioengineering》2009,108(5):429-434
Autotrophic growth of Porphyridium cruentum under 18:12 h and 12:12 h light:dark cycles showed the maximum cell concentration of 2.1 g-dry wt./L, whereas the specific growth rate, 0.042 (1/h), at 18:6 h is faster than that of 12:12 h, 0.031 (1/h), respectively. The highest lipid accumulation level, 19.3 (%, w/w), was achieved at 12:12 h cycle. Under dark cultivation condition with 10 g/L of glucose, the lipid accumulation in the cell was 10.9 (%, w/w), whereas the heterotrophic growth with glycerol as the carbon resource showed low level of cell concentration and lipid production, compared to that of glucose. The glucose was decided to be a suitable carbon resource for the heterotrophic growth of P. cruentum. The lipids from P. cruentum seemed be feasible for biodiesel production, because over 30% of the lipid was C16–C18:1. The cultivation time and temperature were important factors to increase the maximum cell concentration. Extending the cultivation time helps maintain the maximum cell concentration, and higher lipid accumulation was achieved at 25 °C, compared to 35 °C. The fed-batch cultures showed that, under the light condition, the specific production rate was slightly decreased to 0.4% lipid/g-dry wt./day at the later stage, whereas, under the dark condition, the specific production rate was maintained to be a maximum value of 1.1% lipid/g-dry wt./day, even in the later stage of cultivation. The results indicate that the heterotrophic or 12:12 h cyclic mixotrophic growth of P. cruentum could be used for the production of biodiesel in long-term fed-batch cultivation of P. cruentum. 相似文献
255.
Fe(III) impurities, which detract refractoriness and whiteness from porcelain and pottery, could be biologically removed from low-quality clay by indigenous dissimilatory Fe(III)-reducing microorganisms. Insoluble Fe(III) in clay particles was leached out as soluble Fe(II), and the Fe(III) reduction reaction was coupled to the oxidation of sugars such as glucose, maltose and sucrose. A maximum removal of 44-45% was obtained when the relative amount of sugar was 5% (w/w; sugar/clay). By the microbial treatment, the whiteness of the clay was increased from 63.20 to 79.64, whereas the redness was clearly decreased from 13.47 to 3.55. 相似文献
256.
Kang YS Cho YS Yoon SK Yu MA Kim CM Lee JO Pyun YR 《Journal of food protection》2006,69(12):2915-2923
Prevalence of Campylobacter in raw chicken meat and human stools and subsequent antibiotic resistance profiles of the pathogenic isolates obtained from 2000 through 2002 were investigated. Campylobacter jejuni and Campylobacter coli were isolated from 570 of the 923 raw chicken meat samples collected from traditional markets, large retail stores, or department stores in Korea, resulting in the isolation rate of 61.8%. A total of 579 Campylobacter isolates were obtained from raw chicken (36.3% for C. jejuni and 26.4% for C. coli) with the average population of 335.6 CFU/g. From 513 human stool samples, 15 isolates of Campylobacter were detected. Seasonal variation in the quantification of C. coli was not noticeable throughout the year, while the isolation rate of C. jejuni was the highest in September through October (840 CFU/g) followed by that of July through August and May through June in decreasing order, showing a significant seasonal effect (P < 0.05). Contamination of Campylobacter was more severe in raw chicken meat sold in traditional markets than in those sold in large retail stores and department stores. Prevalence of Campylobacter in raw chicken sold in traditional markets was significantly influenced by seasonal changes (P < 0.05), whereas the samples obtained from other places was less affected by the seasonal changes. Susceptibilities of the 594 chicken isolates to ciprofloxaxin, chloramphenicol, erythromycin, kanamycin, nalidixic acid, and tetracycline were determined by an E-test. Campylobacter isolates were the most resistant to nalidixic acid (91.4%) followed by ciprofloxaxin (87.9%), tetracycline (87.2%), kanamycin (30.6%), erythromycin (19.4%), and chloramphenicol (1.3%). Human isolates showed a similar resistance to the six antibiotics tested. The proportion of Campylobacter isolates with multidrug resistance to four or more antimicrobials obtained from 2000 through 2002 ranged from 28 to 43.5%, indicating that it could be a serious health-threatening factor. This study suggests that it is prudent to establish an effective National Monitoring Program in Korea for the prevention and control of Campylobacter spp. 相似文献
257.
Soo-Yeong ParkHee Kyoung Lim Seogjae LeeHyeong Cheol Hwang Somi K. ChoMoonjae Cho 《Food chemistry》2012,132(1):487-492
Pepsin-solubilised collagen (PSC) from Red Sea cucumber (Stichopus japonicus) was studied with respect to its wound-healing effects on a human keratinocyte (HaCaT) cell line. Disaggregated collagen fibres were treated with 0.1 M NaOH for 24 h and digested with pepsin for 72 h to reach maximum yield of 26.6%. The results of an in vitro wound-healing test showed that migration of HaCaT cells was 1.5-fold faster on PSC-coated plates than on untreated plates. The migration rate of sea cucumber PSC was similar to that of rat PSC, but five times higher than that of bovine gelatin. HaCaT cells grown on PSC-coated plates revealed increased fibronectin synthesis (6-fold and 3-fold compared to gelatin and rat PSC, respectively). Additionally, sea cucumber PSCs induced HaCaT cell proliferation by decreasing the G1 phase by 5% and maintaining a larger population (8%) of cells in mitosis. Collagen from Red Sea cucumber might be useful as an alternative to mammalian collagen in the nutraceutical and pharmaceutical industries. 相似文献
258.
This study analyzed polycyclic aromatic hydrocarbons (PAHs) reported to be carcinogenic and listed by the International Agency for Research on Cancer (IARC) as group 1 to 3. Liquid-liquid extraction and HPLC-FLD were used to for the analysis and detection of the 7 PAHs. The average concentrations of total PAHs were 0.435 and 0.457 μg/kg in infant formulas and mixed milk powders, respectively. Furthermore, BaP contents were much lower than 1 μg/kg, the maximum tolerable limit reported by the Commission Regulation. PAH contents were converted to BaP to conduct exposure assessment and risk characterization. Dietary exposure was in the range of 0.037 to 0.073 ng-TEQBaP/kg/day. Margin of exposure (MOE) was from 1,370,000 to 2,700,000, which is of negligible concern. 相似文献
259.
This study aimed to investigate the effects of temperature on the black garlic manufacturing process. The moisture content, pH, browning intensity, S-allyl cysteine (SAC) content and antioxidant activity, including DPPH radical scavenging activity and reducing power, were determined. The moisture content of garlic gradually decreased throughout the heating process. The rate of moisture removal was higher at high temperatures compared with low temperatures. The pH also decreased more significantly in garlic heated at high temperatures. The browning intensity increased with increasing temperature. The SAC contents of black garlic were significantly different according to heating temperature; the garlic samples heated at a low temperature had a higher SAC contents. Antioxidant activity, as determined by the DPPH radical scavenging activity and reducing power, increased when the garlic was exposed to higher temperatures. 相似文献
260.
T.H. Cho B.S. Kim S.J. Jo H.G. Kang B.Y. Choi M.Y. Kim 《Food Additives and Contaminants: Part B: Surveillance Communications》2013,6(1):27-37
Between 2003 and 2005, a total of 11,716 samples were collected and analysed to determine the level of pesticides residues. Multi-residue methods (MRMs) capable of simultaneously determining 250 pesticides were used. Of the 11,716 samples, 89.1% had no detectable residues and 1.7% had violative residues. The detection rates by commodity group were 11.4, 8.6, 0.3, and 0.02% for vegetables, fruit, grain, mushrooms, and the others, respectively. Agricultural products with pesticide residues were pepper, Perilla frutescens, leafy lettuce and spinach in decreasing order. Of the 250 pesticides that were monitored, 70 pesticides were actually found. Procymidone, endosulfan, chlorfenapyr, metalaxyl, and diethofencarb were frequently detected. Of the samples, parsley, Petasites hybridus, Aster scaber and leek had high violative rates of 23.1, 12.6, 8.2, and 7.9%, respectively. From violative samples, procymidone, endosulfan, metalaxyl, diazinon and chlorpyrifos were frequently detected. The violation rates were 1.71, 1.68, and 1.76% in 2003, 2004 and 2005, respectively, and the detection rates were 8.5, 12.0, and 13.3% in 2003, 2004, and 2005, respectively. 相似文献